Woah. You are starting to sound like the 9/11 conspiracy theorists who list their so called "evidence and cite lack of explanations as proof that George Bush and Mossad must have done it. The questions you ask are not the only ones to ask. A crime scene not only tells a story of what is there but also of what is missing. So here are a few for you.
If other people (lets assume they are persons unknown) participated in the brutal rape and murder of this woman, where is the physical evidence of their participation? Not, bleached knives and clothes in washing machines, not "the roses weren't trampled. I mean where is the bloodstained hand prints smeared on the wall of the bedroom. I mean the dna of the perpetrators mingled with the blood of the victim. Evidence of Guedes participation is everywhere in that room. Everywhere. Bloody footprints. DNA. Fingerprints. Palm prints. Body fluids but nothing of others participants. Not a scrap. So we are to believe that persons unknown, participated in the brutal rape and stabbing murder of Kercher. Held her down while she was raped and butchered and yet somehow managed to avoid all evidence of contamination. Not a drop of blood, not a finger print. Not a scrap of DNA. Not a single stain on their clothes. Not a scrap of evidence that they came into contact with any blood. This is impossible. Stabbings are messy, very messy and Kercher was stabbed 47 times!
Or perhaps they cleaned up after themselves? So they managed to clean up every scrap of evidence of their participation, every scrap of contamination, every bloody hand print and finger print and every scrap of dna whilst miraculously leaving evidence of Guide for the cops to find?
Don't be so bloody stupid. Guedes dna, fingerprints, palm prints, bloody foot prints, body fluids etc were there because......
Every other participants dna, fingerprints, bloody palm prints, bloody foot prints, body fluids were entirely absent from that room because.....
But hey, the roses outside the window weren't trampled